Effective and efficient fluid stream processing is one consideration in numerous chemical and industrial processes. An example of such a process involves the removal of materials such as krypton, xenon, and iodine from nuclear fuel treatment off-gas streams prior to discharge or disposal of the fluid stream. Krypton and iodine are generally present in such nuclear fuel treatment off-gas streams as the radioactive isotopes (e.g., krypton-85, iodine-131, iodine-129, etc.) that must be removed to avoid various detrimental environment impacts. Xenon is a rare gas useful in a broad array of commercial applications (e.g., medical applications).
Numerous processes have been developed to separate and enrich materials such as krypton, xenon, and iodine from a fluid stream. For example, an active component, such as a crystalline aluminosilicate material, may be provided to contact the fluid stream and remove at least one of the krypton, xenon, and iodine by way of adsorption. The effectiveness and efficiency of the active component is at least partially a function of the total surface area of the active component that contacts the fluid stream. Larger active component surface areas are capable of removing a greater amount of material from the fluid stream.
Providing the active component in, for example, a powder form or a finely granulated form provides a large surface area of the active component. However, such forms may also induce resistance to flow (e.g., pressure drops), compromising the rate at which the fluid stream is processed. Namely, as particle size is reduced (i.e., as it is when the active component is provided as a powder or plurality of small granules), the size of the air spaces or openings between adjacent particles is correspondingly reduced, decreasing the flow rate of a fluid stream through the particles. The concept is generally expressed by the equation Q=Va, where “Q” is the volume of fluid flow per unit of time, “V” is the velocity of the fluid, and “a” is the area (e.g., air space between adjacent particles) through which the fluid passes.
To resolve the aforementioned flow problems while maintaining a large surface area of the active component, a finely granulated form or a powdered form of the active component may be compressed under high pressure to form relatively larger active component pellets. However, the flow of fluid through the active component pellets tends to wash away some of the active component, reducing the effectiveness and efficiency of the active component pellets over time. In addition, such active component pellets tend to be brittle and crumble over time, which may render them inadequate for fluid stream processing. Thus, active component pellets are not well suited to withstand the conditions that may occur in many industrial environments.
As an alternative to the powdered, finely granulated, and pelletized forms of the active component, a composite media can be provided that includes the active component disposed within a supporting matrix. The composite media elements have a relatively larger, generally spherical shape, enabling large voids to exist between a number of adjacent composite media elements, and reducing the fluid stream flow restriction problems previously discussed. The supporting matrix may be an inorganic material, such as a clay (e.g., kaolin clay, bentonite clay, or attapulgite clay), a silica, or alumina, which is stable under radioactive conditions. The active component is loaded into the supporting matrix. Disadvantageously, however, the inorganic materials conventionally used as the supporting matrix have minimal, if any, porosity, limiting the effectiveness and efficiency of the composite media for processing fluid streams. Namely, the fluid stream is substantially unable to interact with the active component disposed within the bulk of the composite media (i.e., active component not exposed along an outer peripheral surface of the composite media), which results in a low active component surface area and a correspondingly limited ability of the composite media to remove material from the fluid stream.
In view of the foregoing, there remains a need for a composite media including a matrix that is stable in a radiation environment and that is sufficiently porous to facilitate better loading of the active component. Such a composite media would provide a relatively larger surface area of the active component, and would, for example, be beneficial in effectively and efficiently processing fluid streams including at least one of krypton (e.g., radioactive isotopes thereof), iodine (e.g., radioactive isotopes thereof), and xenon.